release: prepare 2.0.0-preview.4

Drain all 14 pending changesets into preview.4 release notes, bump the private root and public packages in lockstep, preserve exact published CLI-to-SDK pairing, and keep package-manager and stable channels held.

Co-authored-by: Data (Squad) <tamirdresher@users.noreply.github.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: 3 people